# Difference between revisions of "Octave"

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Packages can also be managed using Octave's installer. To install a package: | Packages can also be managed using Octave's installer. To install a package: | ||

− | + | octave:1> pkg install -forge packagename | |

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− | octave:1> pkg install | ||

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To uninstall a package: | To uninstall a package: | ||

− | octave:3> pkg uninstall packagename | + | octave:3> pkg uninstall packagename |

Some packages get loaded automatically by Octave, for those which do not: | Some packages get loaded automatically by Octave, for those which do not: |

## Revision as of 20:51, 6 January 2014

Template:Article summary start Template:Article summary text Template:Article summary heading Template:Article summary wiki Template:Article summary wiki Template:Article summary wiki Template:Article summary end From the official website:

*GNU Octave is a high-level interpreted language, primarily intended for numerical computations. It provides capabilities for the numerical solution of linear and nonlinear problems, and for performing other numerical experiments. It also provides extensive graphics capabilities for data visualization and manipulation. Octave is normally used through its interactive command line interface, but it can also be used to write non-interactive programs. The Octave language is quite similar to Matlab so that most programs are easily portable.*

## Contents

## Installation

Octave can be installed with the package octave, available in the official repositories.

## Octave-Forge

Octave provides a set of packages, similar to Matlab's Toolboxes, through Octave-Forge. Some of these packages may be found in the AUR (search packages). A non-exhaustive list:

**Image**— Provides functions for processing images.

**Statistics**— Provides additional statistical functions.

**IO**— Provides input and output in external formats such as XML, CSV or XLS.

**Signal**— Provides signal processing tools, including filtering, windowing and display functions.

**Multicore**— Provides functions for parallel processing on multiple cores.

A complete list can be found on Octave-Forge.

### Packaging

Creating an Octave-forge package for Arch is easy using the Octave-forge helper scripts for Archlinux.

### Using Octave's installer

Packages can also be managed using Octave's installer. To install a package:

octave:1> pkg install -forge packagename

To uninstall a package:

octave:3> pkg uninstall packagename

Some packages get loaded automatically by Octave, for those which do not:

octave:4> pkg load packagename

or

octave:5> pkg load all

To see which packages have been loaded use `pkg list`

, the packages with an asterisk are the ones that are already loaded.

A way to make sure that all packages gets loaded at Octave startup:

/usr/share/octave/site/m/startup/octaverc

## System-wide startup file for Octave. ## ## This file should contain any commands that should be executed each ## time Octave starts for every user at this site. pkg load all

## Plotting

Octave has two official plotting backends:

**Gnuplot**— A classic Linux plotting utility.

**FLTK Backend**— A new experimental OpenGL backend based on the FLTK GUI toolkit.

**Note:**To enable the FLTK backend, you need to install the fltk package.

GnuPlot is still the default, but it can be changed by:

octave:1> graphics_toolkit("fltk");

To make this change permanent add it to your `~/.octaverc`

file.

## Graphical interfaces

There are very few graphical interfaces for Octave and none of them are official:

**Cantor**— A graphical user interface that delegates its mathematical operations to one of several back ends (Scilab, Maxima, Octave and others).

**QtOctave**— A Qt frontend for Octave.

## Reading Microsoft Excel Spreadsheets

There are several ways to read Microsoft Excel files with Octave.

#### Converting to an open format

The easiest way to use `.xls`

files in Octave would be to convert them to `.csv`

or `.ods`

using Calc (limited to 1024 columns) from Libreoffice or Sheets(limited to 32768 columns) from the the Calligra Suite.

After the conversion is complete you can use the build-in Octave function `csvread`

for `.csv`

files:

octave:1> csvread('myfile.csv');

For `.ods`

files the octave-io^{AUR} package is necessary which contains the `odsread`

function:

octave:1> odsread('myfile.ods');

For `.xlsx`

files you can use the xlsx2csv^{AUR} package from AUR:

xlsx2csv -t /path/to/save/location -x /path/to/myfile.xlsx

#### Reading xls files directly from Octave

If you must work with XLS files and you cannot convert them to CSV or ODS, for whatever reason, you can use the `xlsread`

function from the octave-io^{AUR} package.

Since octave-io^{AUR} version 1.2.5., an interface called 'OCT' was added, which perform reading .xlsx, ods and .gnumeric without any dependencies. However, the Java-based interface still exist (special for reading .xls files and writing those file formats).

##### Steps necessary to make Java Interface available

The steps necessary to make it work are:

- 1. Install jdk7-openjdk, available in the official repositories.

**Note:**A common problem is that Octave cannot find the JDK path. To fix this execute the following commands in your shell:

$ export JAVA_HOME=/usr/lib/jvm/java-7-openjdkYou may also want to add this to your

`~/.bashrc`

and append it to your `PATH`

.- 2. Install a Java XLS library for
`xlsread`

. There are more such libraries available, a comparison can be found at here. The recommended library is apache-poi^{AUR}, available in the AUR.

- 3. Finally, install the octave-java
^{AUR}package from AUR.

To check if Java is working correctly in Octave, see the output of:

octave:1> javaclasspath STATIC JAVA PATH - empty - DYNAMIC JAVA PATH - empty -

To load the selected library in Octave, check if it is in the Java path. If not:

octave:1> javaaddpath path/to/file.jar

In the case you chose apache-poi^{AUR}, the relevant JAR files can be found in `/usr/share/java/apache-poi/poi-3.x.jar`

and `/usr/share/java/apache-poi/poi-ooxml-3.x.jar`

.

To check if it works

octave:1> chk_spreadsheet_support

The output should be > 0:

0 No spreadsheet I/O support found ---------- XLS (Excel) interfaces: ---------- 1 = COM (ActiveX / Excel) 2 = POI (Java / Apache POI) 4 = POI+OOXML (Java / Apache POI) 8 = JXL (Java / JExcelAPI) 16 = OXS (Java / OpenXLS) --- ODS (OpenOffice.org Calc) interfaces ---- 32 = OTK (Java/ ODF Toolkit) 64 = JOD (Java / jOpenDocument) ----------------- XLS & ODS: ---------------- 128 = UNO (Java / UNO bridge - OpenOffice.org)

To make this permanent add the `javaaddpath`

commands to your `~/.octaverc`

file.